I. In Vitro Assays for Lactogenic Factors
The extreme complexity of the mammalian hormone environment has made in vitro culture techniques indispensable in elucidating the role of hormones in mammary cell function. Model systems for the study of mammary hormonal control are reviewed by Errick, J.E., et al. ("In Vitro Model Systems for the Study of Hormonal Control of Mammary Gland Growth and Differentiation, in: Lactation Physiology, Nutrition, and Breast-Feeding (Neville, M. C., et al., eds., Plenum Publishing, New York (1983), pp. 179-196)), which reference is hereby incorporated in its entirety. Such systems have been found to be useful in deducing whether a particular factor has an effect on mammary cell function (i.e., lactogenesis, lactation, mammatogenesis, etc.)
One major in vitro model system for the study of hormonal control involves the culture of small pieces of mammary tissue containing a mixture of epithelial cells and stromal cells. Lactogenesis may be assayed, in such ex plante cultures, by measuring the amount of alpha-lactalbumin, a component of the lactose synthetase enzyme, a well-known marker of mammary differentiation, and correlating the amount of alpha-lactalbumin with the extent of lactogenesis (Nicholas, K.R., et al., Biochem. Biophys. Res. Commun. 94:1424-1431 (1980)). Lactogenesis may also be assayed by measuring any characteristic indicator of milk synthesis such as casein synthesis, casein mRNA, lactose, etc.